Self-winding watch barrels



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United States Patent 3,130,538 SELF-WINDING WATCH BARRELS Jean Bourquin, Sao Paulo, Brazil, and Fritz Straumann,

Waldenhurg, Switzerland, assignors to Institut Dr. lug.

Reinhard Straumann A.G., Waldenburg, Switzerland Filed Sept. 26, 1962, Ser. No. 231,314 Claims priority, application Switzerland Jan. 31, 1957 7 Claims. (Cl. 58-87) This invention generally relates to watches and is particularly directed to a barrel-spring construction for self- Winding watches of the type wherein the barrel accommodates both a main or driving spiral spring and an auxiliary spring. In these prior art constructions the outermost turn of the main spiral spring frictionally bears against the inner cylindrical wall of the barrel while the auxiliary spring is secured to the inside of the main spring to urge the main spring against the inner barrel wall. The outermost turn of the main spring and the inner barrel wall thus constitute together a slip coupling. Barrel-spring constructions of this kind are known in the art and have been disclosed, for example, in British Patent No. 766,191, of October 6, 1954. The slip coupling formed by the inner wall of the barrel and the outermost turn of the main spring prevents over winding and thus breakage of the main spring as upon excessive winding the spring slips or glides along the wall surface of the barrel.

It is well known by those skilled in the art of selfwinding watch constructions that the arm movements of the wearer of a self-winding watch during normal wear are more than sufiicient fully to wind the main spring and, in fact, would cause almost constant over winding in the absence of the slip coupling referred to. For this reason, the outermost turn of the main spring performs a large number of sliding movements relative to the barrel wall. Experiments and tests have established that in a customary barrel-spring arrangement of the kind referred to and during normal wear the outermost turn of the spring may perform as numerous as -50 sliding movements per day relative to the barrel wall with a view to neutralizing the over winding tendency .cwsed by the arm movements. In this connection reference is had to a lecture delivered by M. F. Voumard before the Societe Suisse de Chronometrie and published in the Journal Suisse dI-lorlogerie, No. 9-1() of 1961.

In recent years, watch manufacturers have increasingly become aware that the frequent and repetitive frictional movement between the main spring and the inner wall of the barrel results in an inaccurate rate and functioning of the Watch after a relatively short period of time. The reason for this is that in spite of lubrication, the pitting or wearing effect exerted by the moving spring on the inner wall surface of the barrel alters the original frictional force characteristics between the barrel and the spring, thus aifecting the watch rate. In this connection, it should be realized that forty relative movements per day between the spring and the barrel wall corresponds to more than fourteen thousand movements per year and experience has conclusively shown that prior art watch barrel-spring constructions are not capable of successfully withstanding the frictional forces without pitting and abrading, thereby affecting the watch rate.

Various attempts have been made to overcome the pitting problem. Prior to this invention it was generally believed by the experts in this art that the pitting effect is reduced if the barrel material is softer than the spring material, as it was believed that the softer barrel material would give, thus avoiding wear and pitting. Watch barrels. are customarily made of brass while the springs are of steel, and as steel is harder than brass, it

was generally accepted that this combination of mating materials favorable reduces pitting and wear. To obtain a still softer mating surface, it has previously been suggested to insert between the outermost turn of the spring and the inner wall of the barrel a ring of synthetic material or to plate the brass surface of the barrel with a galvanic soft metal layer as, for example, of gold. A barrel spring arrangement with an intermediate ring of synthetic material has been patented, for example, in Switzerland under No. 318,495, in France under No. 1,108,654 and in England under No. 751,461. Extensive tests and experience have, however, conclusively established that the interposition of a relatively soft ring of synthetic material or a layer of a soft metal such as gold does not successfully solve the problem under consideration. With regard to rings of synthetic material it must also be considered that such rings require considerable space. As the available space in a self-winding Watch is most limited, the employment of an additional ring presents considerable, if not unsurrnountable, difiiculties.

In considering the problem of maintaining an accurate watch rate for extended periods of time, it must also be appreciated that for proper and accurate functioning of the watch, the respective magnitude of the frictional force between the spring and the barrel wall is of no great consequence as long as it is constant and Within reasonable limits. Decisive, however, is that the fric tional force value between the spring and the barrel wall remains constant throughout the life of the watch.

The present invention is the result of extensive experiments and research directed toward solving the pitting problem referred to and, therefore, has as its primary object to provide a barrel-main spring construction wherein the frictional force between the main spring sliding relative to the barrel wall remains constant for an indefinite'period of time.

Briefly, the invention resides in the realization that pitting between the main spring and the barrel wall is substantially eliminated if the hardness of the material of the spring is substantially equal or lower than the hardness of the material of the mating wall surface. Under these conditions the Watch rate remains constant for indefinite periods.

According to a particularly advantageous embodiment, the barrel proper consists of aluminum with its inner wall anodized or oxidized in Well known manner.

Although both aluminum and brass can be machined without great difliculty, it is an established fact that prior art watch barrels have always been made from brass and the present invention for the first time realizes the superiority of aluminum barrels having a reinforced, i.e. oxidized or anodized, interior mating surface for the spring.

The present invention successfully overcomes a prejudice which for many years has been accepted in this art to the effect that the material of the watch barrel should be softer than the spring material.

In evaluating this invention it should also be borne in mind that the respective hardness of a material per se is not conclusive with regard to its resistance to pitting or wear. Thus, when two mating surfaces of different materials perform movements relative to each other, it often-times happens that the harder surface is more susceptible to wear than the softer one. In this connection, reference is had to an article entitled Slideway Wear Factors in Machine Tools, as appearing in Engineering, vol. 192, No. 4970 of July 21, 1961. In this article the author states that hardening of one or both elements of a sliding pair has often been practiced on the assumption that it increases wear resistance. The process of wear in machine tools is not, however, a simple one and not only can it not be assumed that hardening increases wear resistance but, in fact, it has been frequently observed that the harder material wears more. The findings of the present invention are therefore unexpected and irrespective of whether the spring and the barrel wall in fact wear to an equal extent, the invention conclusively proves that the frictional force between the spring and the barrel wall surface and the watch rate remain constant for indefinite periods if the hardness of the respective materials is substantially equal.

The watch barrel according to this invention may be made of steel or of an age-hardened non-corrosive alloy. Theoretically brass barrels may still be used, provided that the spring does not mate with the brass surface proper but with a harder material which may be plated or otherwise strongly bonded on the brass. A type of steel suitable for making the inventive barrels, or for the interior of a brass barrel, is a normal hardened carbon steel of a Vicker hardness of about 800 kgs. per mm. Cr/ Ni steel (18/8 steel) may be used which has a Vicker hardness of 700 kgs. per mmP. A hard surface layer may also be obtained by hard chrome plating or by steaming. As previously mentioned, however, a preferred embodiment of the invention is to manufacture the barrel from aluminum or aluminum alloy, the inner hard wall surface of the barrel being obtained by an electrolytic oxidation process. Such oxidized or anodized aluminum surface has a hardness which is at least approximately equal to the hardness of steel springs.

Endurance tests carried out to the breakage point have conclusively established that any pitting caused by the main spring is eliminated.

The main spring may be made of texture-rolled spring steel with a Vicker hardness of 700 kgs. per mm. or of an alloy on a Ni-Co-Cr basis (Nivaflex) with a Vicker hardness of 720 kgs. per mm. If an oxidized aluminum barrel is used the eloxalized layer consists of A1 (sapphire corundum).

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

In the drawings:

FIG. 1 is a top plan view of a watch barrel of a first embodiment with the barrel cover partly broken off;

FIG. 2 is a cross-section on line IIII of FIG. 1;

FIG. 3 is a similar cross-section as shown in FIG. 2 through a barrel of a second embodiment;

FIG. 4 is a diagram representing the spring force of the main spring of a prior art self-winding watch movement in which the barrel is made of brass, the diagram representing the spring force when the watch is new;

FIG. 5 is a diagram corresponding to FIG. 4, after eight thousand movements of the spring relative to the watch barrel;

FIG. 6 is a graph corresponding to FIG. 4 wherein the watch barrel is made of aluminum having an eloxized or anodized inner mating surface in the fresh state;

FIG. 7 is a graph corresponding to FIG. 6, but after eight thousand movements;

FIG. 8 is a graph corresponding to FIG. 6, but after forty thousand movements; and

FIG. 9 is a graph corresponding to FIG. 6, but after two hundred thousand movements.

Referring now to the drawings, and in particular to FIGS. 1 and 2, it will be noted that the watch barrel is indicated by reference numeral :1 while b is the barrel cover mounted on the barrel. The main spring 0 and the auxiliary spring d are accommodated within the barrel a. The auxiliary spring d forces the outermost turn of the main spring 0 against the cylindrical wall of the barrel a. The barrel in this embodiment consists of steel or a steel alloy, the hardness of the surface coacting with the outermost main spring turn being at least equal to the hardness of the material of the main spring 0. In some instances, the outermost turn of the auxiliary spring contacts the cylindrical wall of the barrel and the hardness of the inner barrel surface should therefore also be at least equal to the hardness of the outermost turn of the auxiliary spring.

The barrel a could equally well be made of aluminum or aluminum alloy and the same result would then be obtained by electrolytically oxidizing the inner surface of the barrel wall as seen at a.

If the barrel a is made of brass, a surface covering (plating layer or inserted ring e) may be inserted with pressure fit into the barrel, as shown in FIG. 3. The surface covering e has a hardness equal to that of the spring with which it frictionally coacts. Pitting of the barrel wall is thereby avoided.

The diagrams of FIGS. 4 through 9 have been arrived at in accordance with the teachings of the book Partial Notes for the Watch-Maker, by G. A. Berner, Biel, edition Horlogere 1948, pages 15 through 31. The spring force was determined with a dynamometer as described on the pages referred to. Such diagrams are also elucidated in the Illustrated Professional Dictionary of Horol gy, by G. A. Berner (La-Chaux-de-Fonds, 1961), under number 1313, while the recording dynamometer for effecting the measurements is described under number 1408.

The procedures described in these publications were, however, modified as follows: While in the publications referred to diagrams for an ordinary winding spring whose outer end is secured to the barrel wall are described, the springs measured for the graphs on the figures were made in slip-coupling relation with the barrel wall as previously described. The springs were wound until their outermost turn started to slip along the barrel wall. The stylus of the recording device is then connected and turning of the spring is effected to obtain about seven revolutions. In this manner, the cylinder carrying the recording paper turns counterclockwise and line 1-2 is drawn. If the barrel inner wall is smooth, line 1-2 will be substantially straight. If the wall is pitted or otherwise damaged, the spring will be excessively wound and its release movement will be uneven, causing the formation of high points on the graph. By turning the handle m in the illustration of the dictionary publication in opposite direction, graphs 23--4-5 are obtained. The spring is entirely released at point 5. If the rotational direction of the handle is again changed thereafter and the spring is tensioned, graphs 5--62 are obtained. The dictionary first describes graphs 5-62 and then the graphs 2-3-45. The configuration of the curve -12 indicates the friction condition between spring and barrel inner wall. An unchanged configuration after 10,0 00 windings indicates that the friction conditions have remained constant. Interpretation of the diagram in the light of the teaching of the book referred to clearly establishes that the spring force in FIGS. 6 through 9 remains substantially the same after many thousand movements of the spring relative to the wall, while the spring force of a spring in the brass barrel according to FIG. 5 has materially decreased, resulting in inaccurate time keeping.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

This is a continuation-in-part application of our copending application Serial No. 711,214, of January 27, 1958.

What is claimed is:

1. In a self-winding watch having a barrel, a main J spring and an auxiliary spring, wherein the outermost turn of the main spring is urged by the auxiliary spring against the inner Wall of the barrel and wherein the outermost turn of the main spring and the inner surface of the barrel form a slip coupling for preventing overwinding of the main spring, the improvement which comprises that the mating surfaces between the barrel and the main spring are of materials having substantially the same hardness.

2 In a barrel for a self-winding watch having a main spring and an auxiliary spring, wherein the outermost turn of the main spring is urged by the auxiliary spring against the inner wall of the barrel and wherein the outermost turn of the main spring and the inner surface of the barrel form a slip coupling for preventing overwinding of the main spring, the improvement which comprises a hard layer located on the inner surface of the barrel wall, said layer having a hardness which is at least equal to the hardness of the main spring.

3. The improvement as claimed in claim 1, wherein the mating surface of said barrel is an oxidized aluminum surface, while the mating surface of the main spring is of steel.

4. The improvement as claimed in claim 1, wherein the mating surface of said barrel is an oxidized aluminum surface, while the mating surface of the main spring is of an alloy on a Ni-Co-Cr basis.

5. -In a self-Winding watch, a barrel having a cylindrical inner surface, a spring accommodated within said barrel and having an outermost turn engaging said inner surface, the hardness of said inner surface being at least equal to that of said outermost spring turn.

6. In a self-winding watch as claimed in claim 5, wherein said barrel is of aluminum and said inner surface is formed by electrolytically oxidizing the aluminum.

7. In a self-winding watch, an aluminum barrel having a cylindrical inner surface formed by electrolytic oxidation of the aluminum, a main spring accommodated within said barrel and having an outermost turn, and an auxiliary spring accommodated within the barrel and having an outermost turn, at least one of said outermost turns being in engagement with said inner surface, and the hardness of said inner surface being at least equal to that of said outermost turns.

References Cited in the file of this patent UNITED STATES PATENTS 977,99'4 Austin Dec. 6, 1910 1,677,045 Odom July 10, 1928 1,746,494 Norton Feb. 11, 1930 2,004,829 Ragsdale June 11, 1935 2,089,080 Valentine Aug. 3, 1937 2,342,159 Moran Feb. 22, 1944 2,513,634 Francis July 4, 1950 2,553,337 Shafer May 15, 1951 2,602,338 Opocensky et a1. July 8, 1952 2,663,139 Fink Dec. 22, 1953 FOREIGN PATENTS 751,461 Great Britain June 27, 1956 1,027,880 France Feb. 8, 1953 

1. IN A SELF-WINDING WATCH HAVING A BARREL, A MAIN SPRING AND AN AUXILIARY SPRING, WHEREIN THE OUTERMOST TURN OF THE MAIN SPRING IS URGED BY THE AUXILIARY SPRING AGAINST THE INNER WALL OF THE BARREL AND WHEREIN THE OUTERMOST TURN OF THE MAIN SPRING AND THE INNER SURFACE OF THE BARREL FORM A SLIP COUPLING FOR PREVENTING OVERWINDING OF THE MAIN SPRING, THE IMPROVEMENT WHICH COMPRISES THAT THE MATING SURFACES BETWEEN THE BARREL AND THE MAIN SPRING ARE OF MATERIALS HAVING SUBSTANTIALLY THE SAME HARDNESS. 